Biomimetic Sol-Gel Materials

Carole Aime, Thibaud Coradin, and Francisco M. Fernandes 

The Sol-Gel Handbook Synthesis, Characterization, and Applications, First Edition. 

Publishing Ltd.) (b) The silica frustule of diatoms. (Reproduced from Ref. [232]. Copyright 2008, Japanese Society of Phycology.) 

This chapter was prepared so as to provide key elements that have driven this area of research from living organisms to functional materials, via the physical chemistry of the (bio)molecules-mineral interfaces. It also aims at illustrating how our understanding of biosilicification processes led us to adopt a different point of view on sol-gel chemistry, offering us new perspectives for its development and application. 

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Overall, the field of biomimetic sol-gel materials has proven to be a rich source of fundamental and applied developments over a wide multidisciplinary landscape. It is also an area with a great future ahead of it, which, apart from its scientific and technical interest, will contribute to the current societal and philosophical debates related to the frontiers between the natural and the synthetic worlds and the place of living matter in man-made technology. 

Similarly to the above-mentioned entrapment of proteins by biomimetic routes, the sol-gel procedure is a useful method for the encapsulation of enzymes and other biological material due to the mild conditions required for the preparation of the silica networks [54,55]. The confinement of the enzyme in the pores of the silica matrix preserves its catalytic activity, since it prevents irreversible structural deformations in the biomolecule. The silica matrix may exert a protective effect against enzyme denaturation even under harsh conditions, as recently reported by Frenkel-Mullerad and Avnir [56] for physically trapped phosphatase enzymes within silica matrices (Figure 1.3). A wide number of organoalkoxy- and alkoxy-silanes have been employed for this purpose, as extensively reviewed by Gill and Ballesteros [57], and the resulting materials have been applied in the construction of optical and electrochemical biosensor devices. Optimization of the sol-gel process is required to prevent denaturation of encapsulated enzymes. Alcohol released during the... 

Poly(oxyethylene)-Si02 ormosils have been prepared as an approach to the preparation of biologically active polymer-apatite composites. For this purpose, Yamamoto et al. [72] obtained these Class II hybrids from triethoxysilyl-terminated poly(oxyethylene) (PEG) and TEOS by using the in situ sol-gel process. After being subjected to the biomimetic process to form the bone-like apatite layer, it was found that a dense apatite layer could be prepared on the hybrid materials, indicating that the silanol groups provide effective sites for CHA nucleation and growth. 

Biomimetic Synthesis of Nanoparticles Carbonyl Complexes of the Transition Metals Metallic Materials Deposition Metal-organic Precursors Polynuclear Organometallic Cluster Complexes Porous Inorganic Materials Self-assembled Inorganic Architectures Semiconductor Nanocrystal Quantum Dots Sol-Gel Encapsulation of Metal and Semiconductor Nanocrystals. 

K.A. Mauritz. Organic-inorganic hybrid materials Perfluorinated ionomers as sol-gel polymerization templates for inorganic alkoxides. Materials Science Engineering C-Biomimetic and Supramolecular Systems 6, 121-133 1998. 

Table 19.1 Main sol-gel biomimetic systems involving a molecular catalyst whose physicochemkBl properties drive its nteraction with an inorganic substrate yielding to metal oxide materials with various characteristics.

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